Many technical fields require interconnection of two tubular members such that one of the members is rotatable about the longitudinal axis of the interconnected members. Rotating adapters or fittings are used to provide a rotatable connection between the tubular members, for example, between a rotatable member and a tubular stem. Sometimes, these members carry pressurized fluid, which necessitates sealed connections between the members and the adapter.
Rotating adapters are often used in medical catheterization systems, where tubular catheters are inserted into the body of a patient to remove or introduce fluid. For example, medical personnel sometimes are required to insert a flexible tubular catheter into a blood vessel during surgery, or into the bladder to remove fluids. Such applications require that the flexible catheter be rotatable relative to a stationary fluid carrying manifold, so as to facilitate movement of the catheter into and through the patient's body. The manifold, which typically includes a tubular stem for attachment of the catheter, is then connected to a fluid reservoir located outside the patient's body which serves as a supply of fluid to be injected into the patient, or as a reservoir for fluid withdrawn from the patient. Use of rotatable adapters allows fluid passage while still permitting the required rotation of the catheter relative to the stem during catheter insertion or removal.
Recently, disposable plastic catheterization system adapters have become popular for use in medical catheterization systems. Disposable products avoid problems associated with sterilization of reusable catheterization system parts made of metal. However, some designs of disposable plastic adapters are subject to failure when used with pressurized fluids. Furthermore, some designs require injection molds that include expensive collapsible core pins to remove the molded parts. Moreover, prior art approaches to improving the pressure handling characteristics have increased the complexity and expense of manufacture of disposable catheterization system parts.
For example, the two-piece swivel coupling adapter described in U.S. Pat. No. 4,254,773 to Waldbillig has a flexible lip which snaps over a tapered flange to rotatably connect the adapter and a catheter. The tapered flange is only captured by a thin flexible inwardly directed plastic lip having a recess or undercut for engaging with the flange in a snap fit. At least partially because the plastic lip is not reinforced, this catheterization system is subject to leakage at higher pressurizations of fluid in the catheter.
Although the Waldbillig device is fairly simple to assemble (only a snap-fit is required), its susceptibility to pressure failures makes it undesirable in applications involving higher pressure fluids (the device has only been tested to 700 psi). Moreover, the injection molds for making the inwardly directed lip for capturing the flange likely requires provision of a collapsible core pin in the mold, so that the undercut or inwardly formed recess in the lip can be removed from the mold. This adds to the cost of the injection mold.
One approach to a catheterization system adapter that offers improved pressure handling characteristics is described in U.S. Pat. No. 4,932,114 to Morse. This rotating adapter comprises two plastic pieces that assemble to form a swivel coupling apparatus. To assemble the device, the adapter is mated with a manifold stem such that a ring on the adapter extends beyond a shoulder on the stem. The adapter ring is then rotated on a forming wheel and heated by a heating device to soften the plastic and permanently deform the plastic ring about the shoulder. While this approach offers greater pressure carrying capability, ostensibly operative at pressures up to 1600 psi, expensive equipment is required to affix the adapter to the catheter stem and permanently deform the ring. Thus, adapters made in accordance with this patent are more difficult to fabricate (simple hand assembly is not possible) and thus more expensive.
Accordingly, there is a need for a low cost rotatable adapter that is more pressure resistant than prior art designs, is easy to assemble manually, and does not require special equipment for either manufacturing the injection molded parts or deforming the parts permanently with expensive heating equipment after assembly.